The present invention relates to a mine roof support.
Mine roof supports are known having ground-contacting support members which are arranged in parallelism to one another spaced lengthwise along the mine face, each having a first end portion facing towards the mine face and a second end portion facing away from the mine face. On the second end portions are mounted upright support elements which carry the actual mine roof shield. The reason why the ground-contacting support members are provided as separate elements, rather than a single element, is to make it possible to adjust the mine roof support more readily to particular characteristics of the environment, i.e., of the underground mine passage. The individual support members are always spaced from one another so that the free area between them can accommodate devices for guiding and advancing the mine roof support as a whole, or for conveyor or similar feeding devices. Also, the channel-like regions between the adjacent support members have in effect a self cleaning effect since rubble which collects forwardly of the mine roof supports can be removed rearwardly through these channels.
The end portions of the support members which face the mine face taper in that direction to a flat configuration, so that the mine roof support can be moved forwardly towards the mine face and the flat portions of the support members can extend beneath, for example a conveyor which extends along the bottom edge of the mine face, so that the front edge of the shield is immediately adjacent to the mine face at the upper end of the same.
Under certain circumstances it has been found that the relatively narrow support members are subjected to very strong surface pressures and therefore penetrate undesirably into the floor of the mine gallery. This could be counteracted by connected the individual support members with appropriate braces or the like, but that would block the channels between them and would prevent the rearward removal of rubble and the like. Furthermore, the integration of guiding and advancing devices for the mine roof support into such a structure would then cause considerably difficulties, and an adjustment possibility to compensate for unevenness of the floor of the mine gallery, which presently exists, would be lost.
It has also been found that in the prior-art constructions the shield of the mine roof support tends to "stick" to the mine roof. This makes it possible for the support members to tilt or yield rearwardly about the pivot axis at which the mine roof shield is connected to the upright of the mine roof support structure. In that case, the free front ends of the support members perform a substantially part-circular movement, the center of the circle being formed by the pivot axis at which the upright of the mine roof support is connected to the mine roof shield. As a consequence, this type of construction has a tendency to be largely supported on the free front ends of the support members, which in turn furthers the tendency of the support members to penetrate into the floor of the mine gallery, especially during the advancement of the mine roof support (which is usually of the walking type) towards the mine face. During the subsequent attempt at advancement, i.e., after such penetration, the penetration prevents or at least substantially hinders the further advancement. At the very least, successive advancements cause the free front ends to penetrate successively deeper into the floor of the mine gallery and to gouge deep grooves into it.